package CAS;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;

/***
 * ABA问题 的解决方案
 * 时间错原子引用
 */
public class ABADemo {
    static AtomicReference<Integer> atomicReference = new AtomicReference<>(100);
    static AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1);

    public static void main(String[] args) {

        System.out.println("==============以下是ABA问题的产生 =====================");
        new Thread(() -> {
            atomicReference.compareAndSet(100, 101);
            atomicReference.compareAndSet(101, 100);
        }, "t1").start();

        new Thread(() -> {
            //暂停1秒钟t2线程，保证上面的t1线程完成了一次ABA操作
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(atomicReference.compareAndSet(100, 2019) + "\t" + atomicReference.get());
        }, "t2").start();

        System.out.println("==============以下是ABA问题的解决 =====================");

        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        new Thread(() -> {
            //暂停1秒钟t2线程，保证上面的t1线程完成了一次ABA操作
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName() + "\t第1次版本号 " + stamp);

            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            atomicStampedReference.compareAndSet(100, 101, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1);
            System.out.println(Thread.currentThread().getName() + "\t 第2次版本号" + atomicStampedReference.getStamp());
            atomicStampedReference.compareAndSet(101, 100, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1);
            System.out.println(Thread.currentThread().getName() + "\t 第3次版本号" + atomicStampedReference.getStamp());
        }, "t3").start();


        new Thread(() -> {
            //暂停1秒钟t2线程，保证上面的t1线程完成了一次ABA操作
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName() + "\t第1次版本号 " + stamp);

            try {
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            boolean result = atomicStampedReference.compareAndSet(100, 2019, stamp, stamp + 1);
            System.out.println(Thread.currentThread().getName() + "\t修改成功否" + result + "\t" + "当前实际版本号" + atomicStampedReference.getStamp());

            System.out.println(Thread.currentThread().getName() + "\t 当前实际最新值" + atomicStampedReference.getReference());

        }, "t4").start();


    }


}
